A pre-crash safety (PCS) system has been developed that reduces or prevents damage from a collision between the own vehicle and a target (another vehicle, a pedestrian, a road structure, etc.) that is located ahead of the own vehicle in its direction of travel. The PCS system calculates time to collision (TTC), which is an estimate of the time remaining until the own vehicle collides with a target, based on the relative distance and relative velocity or relative acceleration between the own vehicle and the target. Based on the calculated TTC, the PCS system, for example, uses a notification device or the like to notify the own vehicle's driver that the own vehicle is approaching the target, or activates a braking device in the own vehicle.
A driving assist apparatus disclosed in PTL 1 relates to the PCS system. According to the driving assist apparatus of PTL 1, a risk level is set that indicates the probability of a collision between the own vehicle and a target, and information based on the risk level is presented to the driver.